1. Field of the Invention
This invention relates to an aqueous composition of a fragrance. More particularly, the invention relates to an aqueous composition of a fragrance suitable for use in an air freshener device for dispensing fragrance into the surrounding environment and which composition contains 3-methyl-3-methoxy butanol. The invention also relates to an air fragrance dispensing device of the wick type using such aqueous composition in which the evaporation rate of the fragrance is controlled to dispense the fragrance into the surrounding environment over extended periods of time, as well as into small or large areas.
2. Description of the Prior Art And Problem to be Solved
Conventional wick type air fresheners for dispensing air freshening fragrances from aqueous compositions include three essential components: (1) a reservoir containing the aqueous air freshening fragrance composition; (2) a diffuser or emanating surface from which the fragrance can evaporate into the surrounding environment; and (3) a wick which draws the fragrance composition via capillary action from the reservoir to the diffuser. In some of the wick type dispensers, the wick and the diffuser may be combined into a single molded unit to provide the same functions as the separate wick/diffuser units.
As described in U.S. Pat. No. 4,663,081, the aqueous fragrance mixture may be a true solution, a colloidal solution or a microemulsion, of the fragrance (e.g. perfume). However, since most of the fragrances used as air fresheners are water-insoluble oils or solids, it is generally necessary to include co-solvent and/or surface active agent, usually both co-solvent and surface active agent. The surface active agent is required to solubilize the fragrance in water, and is often present in amounts as high as 10 to 15% or more, by weight, based on the total composition. Since the surfactants, which are most typically anionic in nature, such as alkyl benzene sulfonates, e.g. sodium dodecyl benzene sulfonate, and sodium alkyl sulfates, e.g. sodium lauryl sulfate, or sometimes nonionic, such as ethoxylated alkyl phenols, e.g. ethoxylated nonyl phenol, are themselves substantially non-volatile, they do not evaporate or volatilize from the diffusing surface such that the concentration of the surface active agent on the diffusing surface gradually increases. The surface active agent also tends to clog the capillary wick. Therefore, the surface active agents impede the diffusion of the fragrance in the wick and prevent effective evaporation of the fragrance from the diffusing surface. Consequently, the fragrance which is trapped in the wick and in or on the diffuser, tends to deceive the consumer into believing that the product is still working even after substantially no more fragrance evaporation is taking place. Often, as much as 5 to 25% or more of the original fragrance mixture consisting predominantly of surface active agent and fragrance remains trapped in the diffuser and wick.
Where co-solvents such as ethanol or isopropanol are used, several additional technical problems occur. Co-solvents such as ethanol have a low flash point and, therefore, substantial amounts (e.g. 3 to 15% by weight of the total composition) of flame retardants must be added to the fragrance mixture at additional cost but without enhancing performance (see e.g. U.S. Pat. No. 4,810,690 for use of dimethyl methyl phosphonate as flame retardant for ethanol co-solvent). Some co-solvents also tend to present toxicity problems.
In addition, co-solvents such as ethanol, propanol, etc., tend to evaporate during the initial stages of use, heightening initial fragrance perception, but as fragrance and surface active agent levels begin to become more concentrated the fragrance perception begins to drop off.
For dispensing air freshening fragrance into larger areas or high traffic locations, such as offices, public bathrooms and the like, it is customary to provide a fan blowing on the diffuser surface to facilitate and promote evaporation and fragrance dispersion into the ambient atmosphere. For fragrance solutions using co-solvents and/or surfactants, the fan action preferentially increases co-solvent evaporation rates and exacerbates surfactant clogging of wick and diffuser by drying the aqueous mixture. Also, high surface active agent and co-solvent levels have led to an additional problem of warping of high density polyethylene (HDPE) fragrance reservoirs and delamination of heat sealed polyethylene/aluminum foil covers.
In the aforementioned U.S. Pat. No. 4,663,081 patentees disclose the use of diethylene glycol monobutyl ether (DEGMBE) as a fragrance solubilizer in an aqueous based liquid perfume composition which is substantially free of surface active agent. Patentees report that other glycol ethers, such as diethylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monoethyl ether and the like, evaporate too rapidly or too slowly, and/or tolerate only very small amounts of water. In contrast DEGMBE is stated to have mid-range volatility and the capacity to tolerate far larger amount of water at a specified perfume concentration than any of the other glycol ethers.
However, while improved results may be achieved using DEGMBE as a perfume or fragrance solubilizer, it has been found that, especially at high levels of fragrance, for example 15 to 20%, surface active agents are required to obtain clear homogeneous fragrance solutions with consequent reduction in total fragrance evaporation as described above. In addition, for large scale commercial production, there is an additional problem in that DEGMBE partially degrades to form peroxide when stored in its shipping container and the peroxide present in the DEGMBE tends to oxidize and degrade the fragrance.